- Accepted Paper
Probing SMEFT operators through production with hypergraph neural networks at the LHC
Phys. Rev. D - Accepted 9 November, 2026
DOI: https://doi.org/10.1103/hk4q-htth
Phys. Rev. D - Accepted 9 November, 2026
DOI: https://doi.org/10.1103/hk4q-htth
The production of four top quarks () at hadron colliders constitutes one of the rarest Standard Model (SM) processes accessible at the Large Hadron Collider (LHC) and provides a uniquely sensitive probe of the top-quark Yukawa coupling, of its possible structure, and of new physics encoded in four-heavy-fermion operators within the Standard Model Effective Field Theory (SMEFT) framework. We present a phenomenological study of production in proton-proton collisions at ~TeV, using a Hyper-Graph Neural Network (H-GNN) to discriminate multilepton signal events from the dominant SM backgrounds viz. , , and processes. In the H-GNN architecture each event is represented as a hypergraph whose nodes correspond to reconstructed jets and leptons and whose hyperedges encode higher-order correlations among arbitrary subsets of these objects, allowing the network to learn the many-body kinematic structures that characterize the final state. Combining same-sign di-lepton, tri-lepton, and four-lepton channels following a CMS-like event selection, the H-GNN attains an area under the ROC curve of for the signal and yields a statistical significance of at ~fb. We exploit the improved signal extraction to derive one-parameter confidence level limits on the Wilson coefficients of the dimension-six operators , , , , and . We project the expected sensitivity at the HL-LHC integrated luminosities of and with uncertainty on the background estimation. Finally, the sensitivity reach of H-GNN is compared to the SPANet and Particle Transformer baseline.
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